When I deploy django with postgresql I got this error.
"name or service not known"
Build id is this '45236098-f869-4d4a-8c00-f5e5418fc2c3'

But I found the problem is PGHOST had set ${{Postgres.PGHOST}} in django Variables.
So I updated PGHOST to publice pghost.
Now it works as I expected.

But still, I don't understand why I didn't work.
All of them are in same railway service as I attached image.